Borophosphosilicate glass (BPSG) has been extensively used as the doped silicon oxide layer material for semiconductor wafers, and the BPSG layer is usually formed by atmospheric pressure chemical vapor deposition (APCVD). The BPSG layers are formed for filling gaps between adjacent metal lines in integrated circuits and for interlayer dielectric isolation.
While the APCVD process is performed, not only the semiconductor wafers but the equipment, such as the pipes and tanks, will also be covered by particles and powders. These particles will cluster together and adhere on the surface of the pipe or tank as an extraneous layer. If the pipe is choked up with the extraneous layer and some particles fall down on the semiconductor wafers, the deposition uniformity and thickness of the BPSG layer will be seriously affected. Therefore, the pipes, tanks, covers, and vessels of the APCVD system need to be cleaned (this cleaning procedure is called "preventive maintenance") after a predetermined number of wafers are deposited.
However, cleaning the APCVD system is not an easy task. The pipes and tanks of the APCVD system are usually made of stainless steel. General cleaning solutions can not totally remove all extraneous matters from the stainless devices, and the strong acid solutions, such as hydrofluoric acid (HF), will gradually corrode the stainless devices. Therefore, most manufacturers of the APCVD system advise users to scrub the stainless devices with brushes. Since the shapes of the pipe and tank are usually very complicated, it is hard to scrub out the extraneous matters completely with brushes. Some extraneous matters may still stay on the APCVD system. In order to ensure that all extraneous matters are totally removed, users must waste a lot of time for cleaning the APCVD system and testing whether the APCVD system is completely cleaned or not so that the working hours of the APCVD system is shortened and the cost is increased.
In addition, while the APCVD system is cleaning, particles and toxic gas will be spread into the air. When a maintenance man is brushing the APCVD system, he possibly inhales the harmful air.
It is therefore attempted by the applicant to deal with the above situation encountered with the prior art.